Oxazole trimethinecyanines



Patented Sept. 19, 1939 UNITED STATES OXAZOLE TRIMETHINECYANINES Wilhelm Schneider, Dessau, Germany, assignor, by mesne assignments, to Agfa Ansco Corporation, Binghamton, N. Y.,

Delaware a corporation of No Drawing. Application June 24, 1936, Serial No. 87,038. In Germany December 1'7, 1932 2 Claims. (01. 260-240) My present invention relates to oxazoletrimethinecyanines. It is a continuation in part of my application Serial No. 702,260 filed December 13, 1933.

One of its objects is to provide a new class of oxazole-trimethinecyanines. Another object are the benzoxazoleetrimethinecyanines substituted in the benzene nucleus whether substituted or unsubstituted at the central carbon atom of the trimethenyl chain. Further objects will be seen from the detailed specification following hereafter.

It has already been proposed to use the unsubstituted benzoxocarbocyanine for sensitizing silver halide emulsions. The sensitizing action of this dye for the yellowish green region of the spectrum, however, is very poor; its maximum is in the bluish-green region of the spectrum and the general sensitivity of the emulsions is but feebly increased.

According to this invention, photographic silver halide emulsions are sensitized by incorporating in the emulsion a symmetrical or unsymmetrical benzoxazole-trimethinecyanines' dye which is substituted in one or both benzene rings of the benzoxazole nuclei and may contain a substituent in the trimethine chain linking the benzoxazole nuclei. Suitable substituents for the benzene rings of the benzoxazole nuclei are: alkyl groups, hydroxy groups, alkoxy groups, halogens and amino-groups; the hydrogen atoms of the amino-groups may be substituted by alkyl groups, acetyl groups, propionyl groups or other organic acid radicals.

The substituted dyes used in accordance with the invention have been found to be well suited for the orthochromatic sensitization of photographic silver halide emulsions. As compared with the unsubstituted benzoxocarbocyanines,

they produce a maximum of sensitivity which is displaced towards the long wave region of the spectrum. Furthermore, the aforesaid substitued 'dyes' are distinguished by an increased intensity of sensitization.

The dyes can be prepared according to known methods. For example, symmetrical benzoxazoletrimethinecyanines may be made by condensing a quaternary ammonium salt of a corresponding benzoxazole having in 2-position a methyl group capable of reaction, with a trialkyl ester of orthoformic acid or with an anhydrous salt of formic acid. Unsymmetrical benzoxocarbocyanines may be made by condensing a Z-methylbenzoxazole quaternary ammonium salt with diphenylformamiq ne n p sence o a c a y de t form an intermediate product which'is then condensed with adifferent 2-methy1benzoxazole quaternary ammonium :salt to formthe dye. The symmetrical dyes substituted at the central carbon atom of the trimethenyl chain are obtainable by condensing a z-methylbenzoxa'zole quaternary ammonium salt with a trialkyl-ortho-carboxylic acid ester, and the unsymmetrical dyes substituted at the central carbon atom are obtainable by condsensing a 2-methylbenzoxazole quaternary ammonium salt with :an alkyl ester of an arylated thioimide to an intermediate product and condensing this intermediate product with a different quaternary ammonium-salt. If in the latter case the same quaternary ammonium'salt is usedas it is used for the productionjof the intermediate product a symmetrical 'dye is obtained. Thus the trimethenyl chain may be substituted at the central carbonatom by alkyl, aryl or aralkyl. The substituted benzoxazoles required as parent materials for the manufacture may be obtained by distillation of a correspondingly substituted orthoacetaminophenol, whereby there distil at first water and then thesubstituted benzoxazole. I The dyes are obtainable according ,tothe desired solubility in form of the bromide, iodide, perchlorate, and so on. For sensitizing a silver halide emulsion they are used in a quantity such as is usual for the known sensitizing dyes. This quantity may amount to'about 10 ,to l0 milligrams per kilo of emulsion ready-tor being cast which contains about'9 per cent of gelatin, 4.5 per cent of silver halide, and ftherest water. However, the'invention is not limited to the" quantities just indicated and the most suitable amount can be found in each case bya few comparative experiments. The dyes may be added to the emulsion in the form of solutions. Suitable solvents are the alcohols, for instance methyl alcohol or ethyl alcohol, whichvmay be used anhydrous or diluted with water. The dyes may be incorporated in the emulsion during any stage of its production; however, they are preferably added to the finished emulsion before casting.

The dyes may likewise be added by bathing the finished photographic material in a bath in which the dye is dissolved. Such a'treatment maybe as follows: Thephotographic material to be sensitized is bathed in a solution containing 1 milligram of the sensitizing dye in 50 to 100 cc. of an aqueous solution of methanol of 50 per cent strength for about 5 minutes. The material is then dried, whereupon it is ready for use.

"The following examples describe the manufacture of some sensitizing dyes for use in accordance with the invention and their sensitizing action on a photographic silver halide emulsion:

Example 1.The dye bis-[3-methyl-6-dimethylamino-benzoxazole (2)] trimethinecyanine iodide corresponding With the formula is obtained by heating a mixture of 4 grams of 6- dimethylamino-2-methylbenzoxazole dimethylsulfate, 3 cc. of orthoformic acid and 10 cc. of pyridine to about C. for about 15 minutes. The hot pyridine solution is mixed with a dilute solution of potassium iodide and the dye which separates is filtered off after cooling and recrystallized from alcohol.

The alcoholic solution of the dye has an absorption maximum at a wave length of about 550 up.

A silver bromide emulsion containing about 4 to 5 per cent of silver iodide is sensitized to waves from about 500 to 650 a l with a maximum at about 590 an by incorporation of the dye.

Example 2.--The dye bis-[3-methyl-5-acetylamino-benzoxazole- (2) -pmethyl-trimethinecyanine perchlorate corresponding with the formula a O 6 a 1 i w l H 5 2 2 5 N 3 0 0 3 N 3 1' N H 000 C OCHS CH3 C104 0H3 may be prepared by heating 4 grams of 2-methyl- 5-acetylamino-benzoxazole dimethylsulfate and 3 cc. of triethyl orthoacetate in 10 cc. of pyridine to C. for about 1 hour. The dye is precipitated by the addition of an aqueous solution of sodium perchlorate. The dye is separated by filtration and is recrystallized from alcohol.

The alcoholic solution of the dye has an absorption maximum at a wave length of about 502 all.

A silver bromide emulsion containing about 4 to 5 per cent of silver iodide is sensitized to waves from about 500 to 600 l with a maximum at about 550 by incorporation of the dye.

Example 3.The dye bis-[3-methyl-6-hydroxy-benzoxazole- (2) l-trimethinecyanine perchlorate corresponding with the formula CH3 G104 C a may be prepared by heating 3 grams of 2-methyl- 6-hydroxy-benzoxazole dimethylsulfate, 2 cc. of triethyl orthoformate and 10 cc. of pyridine to 130 C. for about 20 minutes. The dye is precipitated by the addition of an aqueous solution of sodium perchlorate. The dye is separated by filtration and recrystallized from alcohol.

The alcoholic solution of the dye has an absorption maximum at a wave length of about 503 1.141..

A silver bromide emulsion containing about 4 to 5 per cent of silver iodide is sensitized to waves 1 mo- 5 c:

CH: C104 CH3 may be prepared by heating a mixture of 3 grams of 2.5-dimethyl-benzoxazole dimethylsulfate, 3 cc. of triethyl orthopropionate and 10 cc. of pyridine to C. for about 1 hour. The dye is precipitated by the addition of an aqueous solution of sodium perchlorate. The dye is separated by filtration and recrystallized from alcohol.

The alcoholic solution of the dye has an absorption maximum at a wave length of about 496 ,u.,u. A silver bromide emulsion containing about 4 to 5 per cent of silver iodide is sensitized to waves from about 500 to 590 pa with a maximum at about 540 1.0a by incorporation of the dye Emample 5.-The dye bis-[3.5-dimethyl-benzoxazole- (2) ls-thienyl trimethinecyanine perchlorate corresponding with the formula may be prepared by heating 3 grams of 2-methyl- 5-methyl-benzoxazole dimethylsulfate, 4 cc. of triethyl orthothiophenate and 10 cc. of pyridine to 135140 C. for about 1 hour. The dye is precipitated by means of an aqueous solution of sodium perchlorate. The dye is separated by filtration and is recrystallized from alcohol.

The alcoholic solution of the dye has an absorption maximum at a wave length of about 515 [Ll-L.

A silver bromide emulsion containing about 4 to 5 per cent of silver iodide is sensitized to waves from about 515 an to 600 141. with a maximum at about 560 by incorporation of the dye.

Example 6.The dye bis-[3-methyl-6-methoxy benzoxazole (2) ]fi ethyl trimethinecyanine bromide corresponding with the formula may be prepared by heating 3 grams of Z-methyl- 6-methoxy-benzoxazole dimethylsulfate, 3 cc. of triethyl orthopropionate and Idea. of pyridine to 135 C. for about 1 hour. The dye is precipitated by the addition of a solution of sodium bromide. The dye is separated by filtration and recrystallized from alcohol,

The alcoholic solution of the dye has an absorption maximum at a wave length of about 512 [Ll-L.

A silver bromide emulsion containing about 4 to 5 per cent of silver iodide is sensitized to waves from about 515 to 605 ,lL/L with a maximum at about 550 (All.

Example 7.The dye bis[3-ethyl-5.6-dilution of potassium iodide.

methyl-benzoxazole- (2) l-trimethinecyanine idodide corresponding with the formula may be prepared by heating 3 grams of 2.5.6-trimethylbenzoxazole ethiodide, 1.5 cc. of triethyl orthoformate, and 10 cc. of pyridine to 140 C. for about 20 minutes. Then there is added a so- The dye which separates in cooling is filtered ofi and may be recrystallized from alcohol.

The alcoholic solution of the dye has an absorption maximum at a wave length of about 498 1141..

A silver bromide emulsion containing about 4 to per cent of silver iodide is sensitized for waves from about 500 to 560 ,up with a maximum at about 525 ,LL/L by incorporation of the dye.

Example 8.-The dye bis-[3-ethyl-5.6-di-methyl-benzoxazole- (2) l- 8-methyl-trimethinecyanine' iodide corresponding with the formula may be prepared by heating 3 grams of 2.5.6- trimethyl-benzoxazole ethiodide, 3 cc. of triethyl orthoacetate, and cc. of pyridine for about 1 hour to 135C. Then there is added a solution of potassium iodide. The dye which separates in cooling is filtered off and may be recrystallized from alcohol.

The alcoholic solution of the dye has an absorption maximum at a wave length of about 503 ML.

A silver bromide emulsion containing about 4 to 5 per cent of silver iodide is sensitized for waves from about 500 to 565 on with maxima at about 552 ,u L and 523 [ll]. by incorporation of the dye.

Example .9.--The dye bis-[3-ethyl-5.6-di-methbenzoxazole- (2) l-,B-ethyl-trimethinecyanine iodide corresponding with the formula may be prepared by heating 3 grams of 2.5.6- trimethyl-benzoxazole ethiodide, 1.5 cc. of triethyl orthopropionate and 10 cc. of pyridine for about 1 hour to 135 G. Then there is added a solution of potassium iodide. The dye which separates in cooling is filtered oif and may be recrystallized from alcohol.

The alcoholic solution of the dye has an absorption maximum at a wave length of about 506 an.

A silver bromide emulsion containing about 4 to 5 per cent of silver iodide is sensitized for waves from about 500 to 565 [LIL with a maximum at about 535 a by incorporation of the dye.

Example 10.-The dye bis-[3-ethyl-6-methylbenzoxazole- (2) l-trimethinecyanine iodide correwith the formula J C2115 may be prepared by heating 3 grams of 2.6-dimethylbenzoxazole ethiodide, 1.5 cc. of triethyl" orthoformate, and 10 cc. of pyridine to 140 C. for about minutes. Then there is added a solution ofpotassium iodide. The dye which separates in cooling is filtered off and may be recrystallized from alcohol.

An alcoholic solution of the dye has an absorption maximum at a wave length of about 495 mm.

A silver bromide emulsion containing about 4 to 5 per cent of silver iodide is sensitized for waves from about 490 to 580 [14L with a maximum at about 523 a by incorporation of the dye.

Example 11.-The dye bis-[S-ethyl-G-methylbenzoxazole- (2) l-,3-methyl-trimethinecyanine iodide corresponding with the formula may be prepared by heating 3 grams of 2.6-dimethylbenzoxazole ethiodide, 1.5 cc. of triethyl orthoacetate, and 10 cc. of pyridine to 135 C. for about 1 hour. Then there is added a solution of potassium iodide. The dye which separates in cooling is filtered off and may be recrystallized from alcohol.

An alcoholic solution of the. dye has an absorption maximum at a wave length of about 500 u.

A silver bromide emulsion containing 4 to 5 per cent of silver iodide is sensitized for waves from about 500 to 560 [Ll-L with a maximum at about 525 M by incorporation of the dye.

Example 12.The dye bis-[3-ethyl-6-methylbenzoxazole- 2) ]-;8-ethyl-trimethinecyanine iodide corresponding with the formula 7 7 Hac $9 H mm H 1 6 OH' 5 3 2 L '2 3 5 4 Nfa fi 1 V @2115 62 5 may be prepared by heating 3 grams of 2.6-dlmethylbenzoxazole ethiodide, 1.5 cc. of triethyl orthopropionate, and 10 cc. of pyridine to 135 C. for about 1 hour. Then there is added a solution of potassium iodide. The dye which separates in cooling is filtered off and may be recrystallized from alcohol.

The alcoholic solution of the dye has an absorption maximum at a wave length of about 503 ,lm.

A silver bromide emulsion containing about 4 to 5 per cent of silver iodide is sensitized for waves from about 500 to 560 ,u,u. with a maximum at about 525 ,lL/J. by incorporation of the dye.

Example 13.'I'he dye bis- [3-ethyl-6-methoxybenzoxazole-(2) l-trimethinecyanine iodide corresponding with the formula =1 a solution of potassium iodide.

may be prepared by-heating 3- gramsof Z-methyl- G-methoxy-benzoxazoleethiodide, 1.5 grams of triethyl orthoformate, and cc. of pyridine to 140 C. for about 20'minutes. Then there is added The dye which separates in. cooling is filtered offand may be recrystallized from alcohol.

The alcoholic solution of the dye has an absorption maximum at a wave length of about 506 r.

A silver bromide emulsion containing about 4 to 5 per cent of silver iodide is sensitized for Waves from about 500 to 610 with a maximum at about 540 l by incorporation of the dye.

Example 14.-The dye bis-[3-methyl-5-chlorobenzoxazole-(2) ]-trimethinecyanine iodide corresponding with the formula may be prepared by heating 3.5 grams of 2- methy1-5-chloro-benzoxazole methiodide with 1.5 cc. of triethyl-orthoformate and 10 cc. of pyridine at 140 C. for about 20 minutes. Then there is added a solution of potassium iodide. After cooling, the dye which separates is filtered; it may be recrystallized from alcohol.

An alcoholic solution of. the dye has an absorption maximum at a wave length of about 494 A silver bromide emulsion containing about 4 to 5 per cent of silver iodide is sensitized by incorporation of the dye to light of wave lengths extending from those to which the emulsion is initially sensitive to about 550 [1M wave length with a maximum at about 515 IL,-

Example 15.2.75 grams of 2-methy1-benzoxazole ethiodide, 2 grams of diphenylformamidine and 10 cc. of acetic anhydride are heated An alcoholic solution of the dye has an absorption maximum at a wave length of about 490 wt.

The dye renders silver halide emulsions sensitive to light of Wave lengths extending from 500 to 5'70 [LIL with a maximum at about 520 fL/L.

What I claim is:

1. The dye bis-[3-ethyl-5.G-dimethyl-benzoxazole- (2) ]-p-methyl-trimethinecyanine iodide.

2. Benzoxazole-trimethinecyanine salts having the following constitution alkyl 0 alkyl 0- alkyl I i l i l alkyl N GCO- II I alkyl alkyl H alkyl wherein alkyl is selected from the class consisting of methyl and ethyl and wherein R is an anion capable of precipitating the dye.

WILHELIVI SCHNEIDER. 

